The present invention relates to a relatively small linear guide apparatus provided for hydraulic equipment, pneumatic equipment, facilities for manufacturing electronic parts such as semiconductor devices, computer's peripheral equipment, measurings equipment and the like, and more particular to an improvement of ball retainers in the linear guide apparatus.
A linear guide apparatus of this type, as shown in FIGS. 8 and 9, provides: a guide rail 101 elongated in the axial direction; and a slider 102 (also called "bearing") slidably mounted on the guide rail 101. The slider 102 linearly slides in the axial direction relative to the guide rail 101 while being guided by the guide rail 101. Both side surfaces of the guide rail 101 have each at least one ball rolling groove 103 of a half circular cross-section. Each of the ball rolling grooves 103 has a thin escaping groove 111 in the bottom.
The slider 102 is mounted on the guide rail 101 in such a manner that it hangs over the slider 102. That is, the slider 102 is inverted-U-shaped in section, having right and left wings. Each of the right and left wings has in its inner surface a ball rolling groove 104 which is confronted with the ball rolling groove 103 of the guide rail 101, and a ball returning path 105 which is formed of a through hole extending in the axial direction in the wing in such a manner that the through hole is in parallel with the ball rolling groove 104. In addition, the slider 102 has a pair of end caps 102B which are mounted at both axial ends. Each of the end caps 102B has a pair of curved paths 106 which are formed in half ring shapes, in such a manner that they are communicated with the ball returning path 105 and the ball rolling groove 104.
The ball rolling grooves 103 of the guide rail 101, and the ball rolling grooves 104 of the slider 102 form a pair of loaded-ball rolling paths 107. The loaded-ball rolling paths 107, the curved paths 106 in the right and left wings, and the ball returning paths 105 form a pair of endless ball circulating paths 108. A number of rolling balls 109 are fitted in the endless ball circulating paths 108. Hence, as the slider is moved relative to the guide rail 101, those balls 109 are infinitely circulated while being rolled.
The linear guide apparatus is assembled as follows: First the rolling balls are installed in the endless ball circulating paths of the slider 102, and then the slider 102 is mounted on the guide rail 101. Before the slider 102 is coupled to the guide rail 101, it is necessary to prevent the rolling balls from falling away from the ball rolling grooves of the slider 102. For this purpose, ball retainers 110 are engaged with the slider 102 to hold the balls 109 in the ball rolling grooves 104. When the slider 102 is coupled to the guide rail 101 with the balls 109 held by the ball retainers 110, the ball retainers 110 are received in the escaping grooves 111 formed in the bottoms of the ball rolling grooves 103, thus not obstructing the rolling of the balls 109.
Examples of the above-described conventional ball retainer have been disclosed, for instance, by Examined Japanese Utility Patent Publication Nos. Sho. 62-8427 and Sho. 63-26577 (hereinafter referred to as "a first conventional retainer" and "a second conventional retainer", respectively, when applicable).
In the first conventional retainer, the ball retainer 110, as shown in FIG. 9, provides: a linear part 112 which is received by the escaping groove 111 formed in the bottom of the ball rolling groove 103 of the guide rail 101; and a pair of semi-circularly curved parts 113 extending from both ends of the linear part 112. The ball retainer 110 is fitted in the slider 102 so that the pair of semi-circularly curved parts 113 are engaged with recess grooves 116 formed in the inner walls of the half-ring-shaped curved paths 106.
In the second conventional retainer, the ball retainer 120 is of a type as shown in FIG. 10. That is, it is made of a wire material rectangular in section. More specifically, the wire material is such that, in its section, the height is larger than the width. The ball retainer 120 is substantially U-shaped, providing: a linear part 121 which is fitted in the escaping groove formed in the bottom of the ball rolling groove; a pair of bent parts 122 which are extended from both ends of the linear part 121 and bent at right angles in the same direction; and a pair of hooked parts 123 which are extended from both ends of the bent parts 122 and inwardly bent towards each other. The ball retainer 120 is coupled to the slider as follows: That is, it is engaged with mounting holes formed in the end caps by utilizing the elastic forces of the bent parts 122 and the hooked parts 123.
In the above-described first conventional retainer, the length of the linear part 112 of the ball retainer 110 and the axial length of the slider body 102A are unavoidably different from each other. In order to absorb this difference, the recess grooves 116 formed in the inner walls of the half-ring-shaped curved paths 106 of the end caps 102B in which the recess grooves 116 engage the curved parts 113 of the ball retainer 110, are made slightly larger in radius than the curved parts 113 of the ball retainer 110, so that small clearances are formed between the ball retainer and the thin grooves 116. Hence, the ball retainers fitted in the slider are liable to vibrate. In the case of a small linear guide apparatus, this vibration may result in difficulties that the rolling balls fall away from the ball rolling grooves, and the ball retainers interfere with the guide rail.
In the second conventional retainer, the wire material is peculiar rectangular in section; that is, it is not an ordinary wire material. Hence, it is difficult to obtain the wire material, and it is also difficult to accurately form the ball retainer 120 with the wire material. On the other hand, in the case where the length of the slider body is not equal to the length of the linear part 121 of the ball retainer 120, the hooked parts 123 are not smoothly engaged with the mounting holes formed in the end caps. Further, in order to prevent the ball retainer 120 from falling away from the slider, the ball retainers 120 must be retained with side seals attached to the end caps.